1. Field of the Invention
The invention relates to a non-dispersive gas analyzer having a light source, whose light is incident through a measuring cuvette, which contains a measured gas to be analyzed, on a non-selective detector having analysis device connected downstream.
2. Description of the Related Art
In absorption-spectrometric gas analysis, predefined components of a gas mixture (measured gas) are quantitatively determined based on their wavelength-specific absorption of light. For this purpose, the light of a light source is guided through the measured gas to be analyzed onto a detector having an analysis device connected downstream. To obtain a defined absorption path, the measured gas is typically contained in a measuring cuvette. The wavelength range of the light that is used is oriented according to the components of the measured gas to be determined and can extend from the near infrared to the ultraviolet or can lie in-between. In non-dispersive gas analysis, there is no spectral decomposition of the light. Instead, selective, optionally tunable, light sources or selective detectors are used. For example, a non-dispersive infrared (NDIR) gas analyzer typically contains a non-selective infrared radiation source and a selective optopneumatic detector that is filled with the component or components to be determined. In another example, a laser spectrometer contains a selective light source in the form of a wavelength-tunable laser and a detector that is non-selective in the observed wavelength range, e.g., a photodiode. In so-called two-beam devices, the light of the light source is portioned onto the measuring cuvette and a reference cuvette filled with a non absorbing reference or zero gas having a downstream further detector and the differential signal of both detectors is analyzed in the analysis device (J. Staab: “Industrielle Gasanalyse [Industrial Gas Analysis]” R. Oldenbourg Verlag Munich Vienna, 1994, page 83).
The light is typically modulated to obtain an alternating signal in the detector. For this purpose, the light beam can be periodically interrupted using a vane wheel or aperture wheel or the light source can be activated in a pulsed manner.
The use of flash discharge lamps in gas analyzers, in particular xenon flash lamps, which have a broadband emission spectrum from ultraviolet to the near infrared, is known (see, e.g., J. Staab: “Industrielle Gasanalyse [Industrial Gas Analysis]” R. Oldenbourg Verlag Munich Vienna, 1994, page 133).
Thus, EP 0 591 758 A1 and EP 0 195 339 B1 each disclose a dispersive gas analyzer having a xenon flash lamp. The light is spectrally decomposed by an optical grating after being transmitted through the measuring cuvette and directed to a detector line made of photodiodes, for example.
It is known that the light flash generated by a flash discharge lamp has a differing time behavior with respect to the emitted wavelengths. Thus, the duration of the light flash of a xenon flash lamp is shortest in the ultraviolet range and longest in the infrared range (see, e.g., Newport Corporation, Oriel xenon flash lamps, Technical Information, found on Jun. 15, 2010 in the Internet under:
http://support.newport.com/file13store/PDFs/tempPDFs/e5457_Oriel-Xenon-Flashlamp-Systems.pdf).